1. Field of the Invention
The invention relates to a method for producing a finishing layer containing a window, allowing a display element disposed beneath the finishing layer to be observed when used in a portable data storage medium. The invention further relates to a portable data storage medium having an active display element and a method for the production thereof. The invention particularly relates to a chip card having a display.
2. Related Art
Chip cards having displays and methods for the production thereof are known in great numbers. For example, a production method can be taken from WO 2008/147061 A1, according to which a board having electronic components, namely: the display, the IC with a contact pad, a battery, and a pushbutton including required wiring, is placed in a frame and potted with synthetic resin, so that a planar structure is created, the top side of which comprises the display. The synthetic resin is cured and the surfaces are smoothed out. The top and bottom side of the structure thus produced is then finished off by means of a printed cover layer, wherein the top cover layer comprises cutouts leaving the display and the contact pad exposed. Alternatively, the top and bottom sides or only the top side can be finished off entirely by means of a transparent cover layer. The cover layers are bonded to the intermediate structure by the application of high temperature. The known method produces usable cards, but the surface comprising the display comprises a palpable edge all around the display, arising due to the cutout in the cover film. When using a transparent cover layer, on the other hand, it is generally required that alphanumeric information be applied directly to the intermediate structure comprising the display element and the additional components. Obtaining good optical quality is thereby very challenging from the production engineering aspect.
The fundamentals of the function, construction, and production of chip cards are known from the “Handbook of Chip Cards” by W. Rankl, W. Effing, Carl Hanser Verlag Munich, 5th edition, 2008. A chip card having a display can also be found in the book. On the subjects of card materials, installation and construction of components for chip cards, and laminating, which are relevant to implementing the invention, explicit reference is made to the book.
A fundamental problem in the production of chip cards with displays, particularly corresponding to the requirements of the relevant ISO standard 7810, is complying with the maximum allowable thickness. Display elements and the flat/planar batteries that are often associated therewith generally have installation heights that approach the maximum values for card thickness, according to the ISO standards indicated. It therefore often necessary, when producing chip cards with displays, to ensure that the thickness of the card construction above and below the display element is as small as possible. Despite the low installation height available, the display elements are sensitive to pressure and bending, and must be sufficiently protected against pressure and bending loads. The design of the finishing layer located above the display is therefore often most difficult to design.
The object of the invention is to disclose a finishing layer and a method for the production thereof, making the production of a portable data storage medium having an active display element easier, while maintaining sufficient mechanical protection of the display element.